1, double brake system, more safe and reliable. 2. High efficiency, light weight motor, asbestos-free brake system, low energy consumption. 3, stamping steel shell, light and strong, rustproof, corrosion resistant, greatly improve the service life. 4, lightweight, beautiful and durable canvas chain bag, convenient storage chain. 5, with limit switch device, when reaching the limit will automatically stop operation, to prevent the chain out of danger.